WO1995004213A1

WO1995004213A1 - Petrol to gas engine conversion

Info

Publication number: WO1995004213A1
Application number: PCT/AU1994/000439
Authority: WO
Inventors: Colin G. Young
Original assignee: Dynex International Pty. Limited
Priority date: 1993-08-03
Filing date: 1994-08-03
Publication date: 1995-02-09

Abstract

A carburation system for use with gaseous fuels incorporating a flow control valve (5) which utilises the fuel injector output signal (8) from a vehicle's engine management computer to control the valve opening and thus the flow rate of gaseous fuel. The flow control valve (5) comprises a body (9) with a fuel inlet (20) which receives fuel from a pressure regulator and a fuel outlet (21) to a vehicle's air induction system, and a valve member with a head (11) and stem (12), the head (11) resting on a valve seat when the flow control valve (5) is closed. The carburation system and flow control valve (5) are adapted to function when the fuel entering the carburation system is in either the liquid or gaseous state.

Description

PETROLTOGASENGINECONVERSION

This invention relates to a simple means for converting internal- combustion engines using hydrocarbon fuels to internal combustion engines using gaseous fuels, such as methane or ethane (natural gas, or NGV), or propane or butane (liquefied petroleum gas, or LPG), and provides improvements in carburation for these engines, where the term carburation in this context means the process of air/fuel mixture. In addition to spark-ignition engines, the invention relates to improvements in carburation on compression- ignition (Diesel) engines.

The inventor's previous work on gaseous-fuel carburation has included the utilisation of various engine conditions, or signals - such as engine speed, inlet manifold vacuum, temperature, and exhaust gas oxygen content - to be combined electronically and/or mechanically/pneumatically so as to control the instantaneous fuel flow rate, in order to suit the particular operating mode of an engine. Current-model motor vehicles use similar technology to control the flow rate of the liquid (petrol) fuel, usually by means of timed-pulse injectors. The engine management computer re lates the duty-cycle, or the percentage of time, that the injectors are open, with respect to the amount of time that they are closed.

Previous conversion systems however have involved the tedious mapping of different engines, there being no system which can be applied universally to all vehicles. They also require a carburettor or mixer which then present hood clearance and space limitation problems. In addition previous systems have presented problems by restricting air flow into the engine, either to measure the air flow rate or to induce the fuel into the engine, and power loss can arise due to the usual loss of volumetric efficiency. Because of the larger volume flow rate of a gas, compared to a liquid, it has been previously undesirable to use timed pulse injectors directly for gaseous fuel carburation.

It is known that the precise on-off voltage output signal from the engine management computer can be utilised to control a gaseous- fuel carburation system. It is also well known that an injector can be used to inject a small - or pilot - amount of gaseous fuel into a metering device, which can effectively amplify the very small flow rate to produce a known larger flow rate. However because of the larger volume flow rate of a gas, compared to a liquid, it is difficult or undesirable to use timed-pulse injectors directly for gaseous-fuel carburation.

It is an object of this invention to overcome these problems by providing a carburation system which utilises the on-off voltage output signal from the engine management computer, such system being able to be fitted to any fuel injected vehicle, regardless of engine type or capacity, and which can be used with any existing type of Natural Gas or LP Gas pressure regulator. It is a further object of this invention that the carburation system does not require any adaptor and can be quickly and economically fitted to a fuel injection vehicle without any power loss due to the usual loss of volumetric efficiency and providing no impairment of fuel economy or exhaust emissions when a vehicle, having a dual-fuel installation, is running on gasoline.

The invention, in its broadest sense, comprises a carburation system for use with gaseous fuels incorporating a flow control valve which utilises the fuel injector output signal from a vehicle's engine management computer to control the valve opening and thus the flow rate of gaseous fuel.

In a preferred embodiment of this invention, the computer output signal can be used to activate a coil/moving-element device to produce a signal curve (which may well be linear) in relation to the pulsed output signal from the computer.

In another embodiment an electronic circuit - such as a dwell- meter - is used to transform the pulsed output signal from the computer into a steady proportional, or relational, signal that can be used to directly, or indirectly, regulate a motor - either electrical or pneumatic - to control the flow rate of gaseous fuel in response to the instantaneous output signal from the computer.

In order that the invention may be more readily understood we shall describe particular embodiments of the invention in relation to the accompanying drawings in which:

Fig. 1 shows an overall arrangement of a gaseous fuel vehicle system. Fig. 2 shows the preferred embodiment of the carburation system. Fig. 3 shows a second embodiment of the carburation system. Fig. 4 shows a third embodiment of the carburation system. Fig. 5 shows a fourth embodiment of the carburetion system. Fig. 6 shows a typical fuel induction arrangement for the three embodiments. Fig. 7 shows an embodiment of the carburation system, when the gaseous fuel is stored, and induced into the engine, in the liquid form. Fig. 8 shows a schematic diagram of the system of Fig. 7 showing lock off, fuel inlet and outlet ports, and solenoid valves controlling the valve and stem unit inside the flow control valve. Fig. 9 shows the flow control valve adapted for use with fuel in the liquid state.

Fig. 1 is a schematic diagram of the fuel storage, preparation, and carburation elements of a vehicular gaseous fuel system. An engine 1 receives fuel from a storage container 2, by means of a fuel line 7, a safety lock-off device 3, pressure regulating apparatus 4, and the flow control valve 5, which delivers the fuel into the air induction system 6.

The flow control valve 5 is regulated, either directly or indirectly, solely by the fuel injector(s) signal from the engine management computer in three possible ways. This is a major advantage in that no gas mixers or adaptors are needed and, rather than using the pressure drop created by air restriction to induce fuel into the engine, fuel is supplied steadily to the engine at a slight positive, constant pressure through simple hose fittings in the induction air passage.

In this embodiment the pressure regulator 4 supplies fuel at a pressure slightly above atmospheric pressure although this is not essential. While in some instances it may be desirable to vary this outlet pressure, the pressure would normally remain constant for any engine operating conditions.

Fig. 2 illustrates the preferred form of valve 5 in which the (amplified) fuel injector signal is used to directly regulate the displacement, or opening, of the gaseous fuel flow control valve.

The flow control valve 5 comprises a body 9, a fuel inlet 20 which receives fuel from the pressure regulator 4, a fuel outlet 21 which delivers fuel to the air induction system 6, a coil 19, a damping device 15 which consists of a fluid 16 and a seal 17, and an orifice 10, through which a profiled valve 11 and stem 12 moves axially, a biasing spring 14, and guides 13. The coil 19 receives an electric current, which may be amplified and conditioned by an amplifier 18 from the engine management computer petrol injector(s) signal 8.

Whereas a petrol injector has a strong spring to ensure that it closes rapidly after the current stops flowing through its coil, the valve 11 and stem 12 assembly is only lightly biased, by means of gravity and spring 14, and its motion is damped in damper 15 due to the viscosity of the fluid 16 between the stem 12 and the lower guide 13.

The current flowing through the coil 19 is not continuous, but is pulsating in relation to the varying duty-cycle of the fuel injector(s) signal 8. Even so, the valve 11 and stem 12 assembly will be displaced vertically upwards further from its static position, as the duty-cycle signal 8, and therefore the percentage of time that current is flowing through the coil 19, increases.

Thus the annular opening area between the orifice 10 and the valve 11 will increase as the duty cycle of the fuel injector(s) signal 8 increases. It will be obvious that the valve 11 can be sized to suit the displacement of the engine 1 with which the carburation system is operating. It will also be obvious that the valve 11 can be profiled as desired, so as to control the flow rate of gaseous fuel in relation to the duty-cycle of the fuel injector(s) signal 8. The fuel injectors do not operate when the engine 1 is running on a gaseous fuel, but the computer still functions. It is desirable to design the profile of the metering valve 11 such that for any particular engine operating condition (engine speed and inlet manifold pressure), the duty-cycle created by the engine management computer is the same as would be created when the engine was running on hydrocarbon fuels. This overcomes potential problems of running satisfactorily on both fuels in a dual-fuel system, due to the computer's "self-teaching" ability.

Fig. 3 is a schematic diagram of a second embodiment of the invention in which a stepper-motor 23 is used to control the valve opening. A position sensor 24, which may use variable luminescence, capacitance, resistance or inductance or any other appropriate means to sense the displacement of the valve 11 and stem 12 assembly, produces a signal, such as a d.c. voltage, in relation to this displacement.

The fuel injector(s) signal 8 is transformed into a compatible signal by a converter 22. Typically, as the effective duty-cycle can lie between zero and 100%, the converter 22 output signal would progressively increase from zero to 12 volts d.c. A comparator device 25 continually compares the signals from the position sensor 24 and the converter 22, and accordingly activates the stepper-motor 23 in the required direction, so that the two signals are driven toward equality. Again it will be obvious that any desired relationship between gaseous fuel flow rate and fuel injector(s) signal 8 can be obtained. Fig. 4 illustrates a third embodiment of the invention in which the fuel injector(s) signal 8 indirectly controls the opening of the flow control valve 5. Again, a position sensor 24, with a sender 34 and a receiver 35, is used to instantaneously determine the displacement of the valve 11 and stem 12 assembly, and a comparator 25 receives the two signals, as in the Fig. 3 arrangement. Rather than use a stepper-motor, the comparator 25 selectively activates two solenoid valves 30 and 32. The valve 11 and stem 12 assembly is controlled by a diaphragm assembly 28, which moves between a lower cover 27, and an upper cover 26, the latter being part of, or attached to, the valve body 9. A control chamber 29 is formed between the diaphragm assembly 28 and the lower cover 27. The valve 30 can receive pressurised gas from the pressure regulator 4 via inlet port 31, while the valve 32 can discharge gas from chamber 29, into the air induction system 6, via outlet port 33.

Again, the comparator 25 always acts to ensure that its two input signals move toward equality, and does so in this arrangement by controlling the amount of gas in chamber 29, the pressure acting on diaphragm assembly 28, and consequently, the displacement of the valve 11 and stem 12 assembly. It will again be obvious that any desired relationship between gaseous fuel flow rate and fuel injector duty-cycle can be achieved.

An alternative to using the converter 22 in the embodiments shown in Fig. 3 and Fig. 4, employs a small, vertical coil/stem/damper assembly - similar to that shown in Fig. 2 - whereby the unaltered computer-generated fuel injector(s) signal 8 passes through the coil. The upper end of the stem moves within a position sensor 24, which again provides a signal in relation to the instantaneous displacement of the stem. Because the coil is only acting as a translator, or injector simulator, and does not have to withstand large gas forces, it can have a low current draw, such that it would not damage the engine management computer.

Figure 5 illustrates a fourth "pilot- valve" embodiment of the invention which allows for extreme flexibility in producing any desired fuel metering curve, in relation to the fuel injector duty-cycle, and provides improved response. An injector (solenoid valve) 30 functions as in the Fig. 4 embodiment but is activated solely by the fuel injector computer signal 8. The signal 8 may also be used via a reversing relay (or solid state equivalent) 50 to activate a second injector (solenoid valve) 32 to control the bleeding of fuel from the chamber 29 into the air induction system 6.

The reversing relay 50 may incorporate a transducer or switch that is activated by a signal 49 which is indicative of the inlet manifold pressure. Such means are well known and not part of the invention. More specifically the rate of change of manifold pressure may be used to modify or override the fuel injector computer signal 8 so that, for example, when the manifold pressure rises rapidly (such as when the driver presses the accelerator pedal quickly), valve 32 will remain closed for a certain period of time, and when the manifold pressure drops rapidly, valve 32 will remain open for a certain period of time. It is obvious that a pneumatically controlled valve could be used instead of the solenoid valve 32.

It may be desirable in some applications to incorporate a damping device 15 as used in the Fig. 2 embodiment. While a diaphragm assembly could be used it is preferable to use a piston 51 to control displacement of the valve 11 and stem 12 assembly. The relationship between the piston 51 displacement and the fuel injector duty-cycle can be controlled by regulating the flow of gas into and out of the chamber 29.

A typical variable bleed means is shown as a series of holes 52 into which tapered screws (not shown) could be adjusted and secured. Such means may be used on either the inlet or outlet port of the chamber 29, or both. An alternative means would be to form stem 12 into a variable cross-section member and to have the chamber 29 outlet port located above the fluid 16 in the wall of the damping cylinder 15. It will be apparent that any relationship between effective port cross-sectional area and piston 51 displacement can be devised.

Fig. 6 shows a typical arrangement for transferring the gaseous fuel from the flow control valve 5 into the air induction system 6. While perhaps not essential, it is desirable to have the fuel enter the engine as close as possible to, and symmetrical with, the throttle valve(s) 37. Because the fuel is supplied at a positive pressure, it is not necessary to use a venturi to induce fuel flow into the air induction system 6, but it is, of course, possible if required. Normally the system would use simple hose fittings 36 to receive the fuel from the flow control valve 5, and direct it uniformly into the engine 1. It may be desirable to utilise some diffusing means 38 on the outlet of the fitting(s) 36, to promote mixing of the fuel with the air in a homogeneous manner. The diffusing means could, for example, be a number of radial or angled holes, serrations, or other objects designed to more evenly disperse the fuel into the air stream.

Figures. 7, 8 and 9 illustrate the carburation system receiving LP Gas or (liquefied) natural gas (LNG) in the liquid state instead of the usual gaseous state. Major advantages associated with using the fuel in this state are the elimination of the need for a vaporiser, and the significant power increase and reduced pre- ignition potential due to the cooler, and hence more dense, induction air. The carburation - or continuous-flow injection - system acts as an open-chamber heat-exchanger, where the heat from the induction air is utilised to vaporise the liquid fuel.

Fig. 7 is a schematic diagram of the general arrangement of the system, where it may be desirable to route the fuel passage 7, from the lock-off 3 to the flow control valve 5, to inside the air induction passage 6, using a typical serpentine configuration 44, so that the fuel entering the flow control valve 5 will have been cooled by the previous vaporising fuel.

Fig. 8 is a schematic diagram of the configuration of the lock-off 3, the fuel inlet port 20, the fuel outlet port 21, and the three solenoid valves 39, 40 and 41, that control the displacement of the valve 11 and stem 12 assembly, inside the revamped flow control valve 5.

Fig. 9 shows the flow control valve 5 adapted for use with fuel in the liquid state, with corresponding designations to those used in the previous Figures. In a like manner, the longitudinal displacement of the metering valve 11 and stem 12 assembly is monitored by a position sensor 24, typically comprising a sender 34 and a receiver 35, and is controlled by regulating the amount of liquid fuel in the chambers 45 and 46.

While it is practicable to use a diaphragm assembly, it would be preferred to have the metering valve 11 and stem 12 assembly and the bore of the body 9 formed as a piston and cylinder arrangement. It is not essential to have perfect sealing between the piston and bore as the control system continually acts in a feed-back mode to correct any undesired variations in the valve 11 displacement. It is also not essential to incorporate the third valve 41 if there is sufficient clearance to allow fuel to pass between chamber 46 and the fuel outlet 21, but it would be preferable to do so. Like the comparable embodiment shown in Fig. 4, solenoid valves 39, 40 and 41 are controlled by the comparator 25, so that displacement of the metering valve 5 is always in a known and precise relationship to the fuel injectors duty-cycle signal 8. Because the fuel pressure at the inlet 20 of the flow valve 5 may vary it may be desirable, to prevent any unwanted adverse self- teaching actions by the engine management computer, to incorporate a compensating means so that the signal received by the comparator 25 from the position sensor 24 is representative of the fuel flow rate from outlet 21 of the flow control valve 5 rather than being representative of the metering valve 11.

This compensating means could well be a simple hydraulic piston and spring device to vary the location of the position sensor 24 from the body 9 in accordance with the fuel inlet pressure. It would be preferable to modify the output signal from the receiver 35 of the position sensor 24 by using a pressure transducer 47 in accordance with the fuel inlet pressure 48. Thus the comparator 25 would always maintain the desired fuel flow rates regardless of the fuel inlet pressure to the flow control valve 5. If the fuel pressure increased the valve opening would be decreased, and if the fuel pressure decreased the valve opening would be increased.

In some applications it may be desirable to prevent ice accumulation on or near the outlet 21 of the flow control valve or the metering valve 11. While the components would normally be smooth and coated with a substance to inhibit the adhesion of ice, it may be necessary to install a heating device of some kind. A temperature probe 42 can then be used to detect and activate the removal of icing conditions. Such thermostatic controls are widely known.

It is possible to adapt a manually operated version of the liquid injection embodiment of the invention for use on a compression ignition (diesel) engine to advantage when running on a bi-fuel system. Alternatively the electronically controlled embodiments for both gaseous and liquid fuel systems can be adapted to regulate the gaseous flow in any desired relationship to the diesel fuel flow rate by substituting a signal from the diesel fuel system in lieu of the fuel injector duty-cycle signal. Such switching means are common knowledge as in bi-fuel systems it is desirable to prevent any gaseous fuel flow when the engine is cold or when the engine is operating at low speeds.

Normally the flow rate of diesel fuel is decreased as the flow rate of the gaseous fuel is increased. The safe limit depends on the design and construction of the particular engine, especially the shape of the combustion chamber and the injection timing, and on the instantaneous operating mode. As with the fuel pressure compensator 47 discussed above it will be apparent that the output signal from the position sensor 24 on the flow control valve 5 can be modified by a signal indicative of the diesel fuel flow rate, or the position of an accelerator pedal, so that the comparator 25 will continually enable the flow control valve 5 to provide any desired gaseous fuel flow rate.

The invention can be adapted to combine both the gaseous fuel and the liquefied fuel versions in an automatic change over system, where the gaseous fuel version is used when , for example, increased engine power is required.

The invention is not limited by the embodiments discussed and it is envisaged that it will encompass further variations falling within the spirit and scope of the invention.

Claims

The claims defining this invention are as follows:

1. A carburation system for use with gaseous fuels incorporating a flow control valve which utilises the fuel injector output signal from a vehicle's engine management computer to control the valve opening and thus the flow rate of gaseous fuel.

2. A carburation system as claimed in claim 1 in which the flow control valve comprises a body with a fuel inlet which receives fuel from a pressure regulator and a fuel outlet to a vehicle's air induction system, and a valve member with a head and stem, the head resting on a valve seat when the flow control valve is closed.

3. A carburation system as claimed in claim 2 with a biasing spring which applies a restoring force to the valve member towards the valve seat.

4. A carburation system as claimed in claim 3 in which the stem of the valve member moves axially within a well of damping fluid, said well being surrounded by a solenoid coil, as an electric current is applied to the coil.

5. A carburation system as claimed in claim 4 in which the fuel injector output signal is amplified and the amplified signal is used to directly regulate the opening of the gaseous fuel flow control valve.

6. A carburation system as claimed in claim 5 in which the valve member is profiled to provide the required flow rate of gaseous fuel in relation to the duty cycle of the fuel injector output signal from the said engine management computer.

7. A carburation system as claimed in claim 3 in which the displacement of the valve member stem within the body of the flow control valve, and thus the valve opening, is measured by a position sensor which produces a signal in proportion to this displacement.

8. A carburation system as claimed in claim 7 in which the fuel injector output signal is converted into a signal compatible with that of the position sensor and which system has a comparator which causes a stepper motor to be activated to drive these signals towards equality and to thereby change the displacement of the valve.

9. A carburation system as claimed in claim 3 in which the displacement of the valve member stem within the body of the flow control valve, and thus the valve opening, is measured by a position sensor which produces a signal in proportion to this displacement and in which the valve member is moved by a diaphragm located within a chamber within the flow control valve, said chamber having an inlet valve from a pressure regulator and an outlet valve to the vehicle's air induction system.

10. A carburation system as claimed in claim 9 in which the fuel injector output signal is converted into a signal compatible with that of the position sensor and which system has a comparator which selectively activates said inlet valve and said outlet valve and drives these signals towards equality and thereby changes the displacement of the valve.

11. A carburation system as claimed in claim 7 and claim 9 in which the stem of the valve member moves axially within a well of damping fluid in a position sensor, said well being surrounded by a coil, through which the unconverted fuel injector output signal passes directly.

12. A carburation system as claimed in claim 9 in which said inlet valve is activated solely by the fuel injection output signal .

13. A carburation system as claimed in claim 12 in which said fuel injection output is used via a reversing relay to activate said outlet valve to and to control the transfer of fuel from said chamber into a vehicle's air induction system.

14. A carburation system as claimed in claim 13 whereby said reversing relay includes means which can be activated by a signal from a vehicle's inlet manifold pressure such that said manifold pressure controls the opening of said flow control valve.

15. A carburation system as claimed in any preceding claim in which any desired relationship between gaseous fuel flow rate and fuel injector duty-cycle can be achieved.

16. A carburation system as claimed in any preceding claim in which the flow control valve is adapted to function when the fuel entering the the carburation system is in either the liquid or gaseous state.

17. A flow control valve for use with gaseous fuels which utilises the fuel injector output signal from a vehicle's engine management computer to control the valve opening and thus the flow rate of the gaseous fuel.

18. A flow control valve as claimed in claim 17 comprising a body with a fuel inlet which receives fuel from a pressure regulator and a fuel outlet to a vehicle's air induction system, and a valve member with a head and stem, the head resting on a valve seat when the flow control valve is closed.

19. A flow control valve as claimed in claim 18 with a biasing spring which applies a restoring force to the valve member towards the valve seat.

20. A flow control valve as claimed in claim 19 in which the stem of the valve member moves axially within a well of damping fluid, said well being surrounded by a solenoid coil, as an electric current is applied to the coil, the opening of the valve to gaseous fuel flow being controlled by the fuel injector output signal of a vehicle's engine management computer.

21. A flow control valve as claimed in claim 20 in which the valve member is profiled to provide the required flow rate of gaseous fuel in relation to the duty cycle of the fuel injector output signal from the said engine management computer.

22. A flow control valve as claimed in claim 19 in which the displacement of the valve member stem within the body of the flow control valve, and thus the valve opening, is measured by a position sensor which produces a signal in proportion to this displacement.

23. A flow control valve as claimed in claim 22 in which the displacement of the valve member is effected by a comparator which causes a stepper motor to be activated to drive the fuel injector output signal towards equality with that of the position sensor.

24. A flow control valve as claimed in claim 19 in which the displacement of the valve member stem within the body of the flow control valve, and thus the valve opening, is measured by a position sensor which produces a signal in proportion to this displacement and in which the valve member is moved by a diaphragm located within a chamber within the flow control valve, said chamber having an inlet valve from a pressure regulator and an outlet valve to the vehicle's air induction system.

25. A flow control valve as claimed in claim 22 and claim 24 in which the stem of the valve member moves axially within a well of damping fluid in a position sensor, said well being surrounded by a coil, through which the unconverted fuel injector output signal passes directly.

26. A flow control valve as claimed in claim 24 in which said inlet valve is activated solely by the fuel injection output signal and said fuel injection output signal is used via a reversing relay to activate said outlet valve and to control the transfer of fuel from said chamber into a vehicle's air induction system.

27. A carburation system as claimed in any preceding claim in which any desired relationship between gaseous fuel flow rate and fuel injector duty-cycle can be achieved.

28. A carburation system as claimed in any preceding claim in which the flow control valve is adapted to function when the fuel entering the the carburation system is in either the liquid or gaseous state.

29. A flow control valve as claimed in any preceding claim in which the flow control valve is adapted to function when the fuel entering it is in either the liquid or gaseous state.

30. A carburation system substantially as hereinbefore described in relation to the accompanying drawings.

31. A flow control valve substantially as hereinbefore described in relation to the accompanying drawings.

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